Yes, i want to write because this is a part of my program.
really the code which you supported dosnt work. at the moment my compter is connected to home group via wireless and also a device is connected to my computer via ethernet port. my computer ip for wireless is 192.168.1.7 and for ethernet is 10.0.0.100
the connecterd devices to wireless: another computers: 192.168.1.2 to 6
the connected device to lan 10.0.0.241

As I see, your question is wrong. What you want is not the list of devices connected to your computer, you want to list the devices connected to your networks. That is something else.
A device is connected to your computer if there is any socket opened between the remote device and your machine, that is what you can list this way, and that is what you asked for.

Well, that's only a little bit more difficult. You have two possibilities:
1) If your router is capable of such reports, you can ask it.
2) If you have the address range, and that is low (as I see, you have two ranges with less than 255 addresses), you can try to ping all addresses one by one supposing that the devices are responding to icmp packets. Use: http://msdn.microsoft.com/en-us/library/system.net.networkinformation.ping.aspx
2+) Here you have a little bit more delicate "nmap" like application, with c# source, you can get ideas: https://github.com/Simran/nmap-csharp